Official AQA GCSE Biology Unit 2 22nd Janurary NEW SPEC

What grade was 34?
& don't worry, stay positive!
The unofficial mark scheme is what I think the answers were, I didn't take this exam, just my first time. But I did take b1, c1 and p1 which is why I made a mark scheme for this because I sort of know what keywords the examiners are looking for

made a few changes:

UNOFFICIAL MARK SCHEME AQA GCSE BIOLOGY UNIT 2
CREATED BY THATGIRLX
(with help from IsaacIIV)


1a) heat is given off by the lamp, how can this problem be solved?
• A glass sheet or glass is placed between the pondweed and lamp to deflect or absorb the heat. OR a water bath (1)
1b) Explain the relationship between distance from lamp, and bubbles given off per minute.
• As the distance increases the oxygen bubbles given off decrease. At 10 and 15cm, the oxygen bubbles remain at 84 meaning that it is no longer the limiting factor (1)
1c) What was preventing photosynthesis?
• Carbon dioxide, concentration or temperature (1)


2a) QWC question: explain the structure and function of a leaf?
• waxy cuticle - reflect UV radiation
• mesophyll - spongy for gas exchange
• xylem + phloem - transport of water and nutrients
• Epidermal tissue - protection, retain shape?
• palisade cells - primary source of photosynthesis
• stomata + guard cells - gas exchange




Enzymes section
1) Explain the relationship between amount to trypsin and rate of reaction?
• As the percentage of trypsin increases, the rate of reaction increases from 0.1 to 0.6. They are directionally proportional to each other. (2)
2) Forgotten question...
• 0.6 or 6% forgot.. (1)
3) Why did the manufacturers use 0.5% trypsin at 35 degrees C?
• It was better for manufacturers to use 0.5% with 35 degrees because 35 is the optimum temperature. So less money is used to maintain higher temperatures for no reason AND because less money is spent on the enzymes which are very costly, a compromise between the two.(4)
4) Why are protease used in the manufacture of baby foods?
• Enzymes are used in baby foods as proteases as they can break down the protein to amino acids. This allows the baby to digest the food easily (3)
5) How is one other enzyme used in industry?
• BIOLOGICAL DETERGENTS: Proteases and lipases are used in industry to remove stains from clothing.
• SLIMMING FOODS: Isomerase can be used to convert glucose syrup into fructose syrup. Fructose is sweeter so less can be used compared to glucose. (3)
• Converting starch to sugar


Mitochondria section
1) Label part A of the plant cell?
• Part A was a mitochondria (1)
2) What chemical reaction takes place here? (I think)
• respiration
3) Explain how oxygen gets to part A?
• Oxygen diffuses from an area of high concentration in the blood to an area of low concentration in the cell. It moves down the concentration gradient through a partially permeable membrane. (4)
4) How do part a and ribosomes work together to produce enzimes.
• Ribosomes produce proteins. They get the energy to do this by Part A the mitochondria respiring to supply energy. They put amino acids in a specific order to form an enzyme (3)


Meiosis section
1) What does this diagram show?
• The diagram showed meiosis (1)
2) Where are the male gametes found?
• Testes (1)
3) How many chromosomes are found in gametes
• 23 (1)
4) Why are there this number?
• They must be 23 so that the gametes produced by meiosis can fuse at fertilisation to produce the full set of 46 whilst causing variation in the offspring. (2)


Genetic variation section:
1) What is a dominant allele?
• A dominant allele is one which is expressed over recessive even if only one is present (1)
2) How can you tell that person B is heterozygous?
• Had children both with + without disorder
3) What genotype was person A?
• Heterozygous! Dd. (1)
4) How can you tell it isn't a recessive disorder?
• You could tell that it was not a recessive disorder because there were no carriers without the disorder (1)
6) Work out the chance of person c+d's child having the disorder?
•50% - drawn genetic cross (4)
7) Why can stem cells be used to treat disorders?
• Stem cells can be made to differentiate to any cell. Therefore can treat the disorder (2)
8) Why is it preferable to take stem cells from umbilical chords rather then embryos?
• Taking cells from skin have no ethical issues / not harmful / optional / volunteers / does not result in death of embryo. (1)


Quadrat section
1) Forgotten question?
•They had to use a large sample size
2) explain why the scientists method were not valid?
• They had to make sure the quadrates were randomly placed (the transect must have been placed anywhere in the woodland, not specifically where they think they would get best results) (2)
2) Explain why the plants in the bright forest grew more flowers than the plants in the dark forest?
The plants in the light can photosynthesise more, meaning growing more compared to the rest (2)
3) Forgotten question?
11 I think, forgot! (1)
4) How could the scientists test their hypothesis?
To test their hypothesis they could place similar sized plants of the same species in both light and dark conditions within the lab, and compare the growth.
5) Why did plants group A grow more flowers?
How plants produce more flowers i have no idea? More photosynthesis occurs, so more glucose produced for growth?(2)


Speciation section
1) Define the term 'species'?
• A species is a group of organisms with similar characteristics who can interbreed to produce fertile offspring (2)
2) Explain why the two plant groups can no longer interbreed even though they were once the same plant species?
• The two groups were separated + isolated; by a geographical barrier (e.g. ocean). Genetic variation occurred, and due to different environments, natural selection occurred differently, the 2 groups became so different that speciation occurred + they cant't interbreed anymore.

For the first question, can 'light intensity' be accepted as an answer?

2) explain why the scientists method were not valid?

I don't remember this question at all, but I remember a question asking how they could make them more valid

I don't remember this question at all, but I remember a question asking how they could make them more valid

I don't remember this question at all, but I remember a question asking how they could make them more valid

That is probably one of the many questions i'de forgotten, i'll add it in..
I didn't actually write most of this mark scheme... i just added any questions i could remember in. Best ask ThatGirlX if she's certain about that question.

Having said that, i think i remember the question more as:
We're told of the scientist method in which the scientist selectively choose areas of woodland and count the organisms there, why is this not a valid method of sampling an area?

Yes, that was the question. I didn't add in the questions Isaac did. The answer was what it said in the unofficial mark scheme: large sample size, random placing of transect/quadrat etc.


This was posted from The Student Room's iPhone/iPad App

Oh, and I said they ought to standardise the counting method - i.e. everything which is half in doesnt count and they should place the transects and quadrats randomly

That is probably one of the many questions i'de forgotten, i'll add it in..
I didn't actually write most of this mark scheme... i just added any questions i could remember in. Best ask ThatGirlX if she's certain about that question.

Having said that, i think i remember the question more as:
We're told of the scientist method in which the scientist selectively choose areas of woodland and count the organisms there, why is this not a valid method of sampling an area?

Yep that's right!

I found the grade boundaries: http://store.aqa.org.uk/over/stat_pd...OUND-JAN13.PDF

A* - 48
A - 39
B - 30
C - 22
D - 14